Illness

A state of being unwell or experiencing impaired health, often as a result of a disease, disorder, injury, or other health problem.

Illness often emphasizes the person’s experience of being unwell, including symptoms and effects on everyday life. It can be caused by a recognized disease, but a person can experience illness even when the underlying cause has not yet been identified.

The term is broader and less technically specific than many diagnostic terms.

QUICK FACT

Illness does not necessarily mean that a specific disease has been diagnosed.

COMMONLY CONFUSED WITH

Disease: Disease generally refers to an identifiable pathological condition or process, whereas illness emphasizes the experience or state of being unwell.

SEE ALSO

Clinical & Educational Context

Discussed in Health Articles & Guides

Explore how "Illness" is covered across our evidence-based editorial guides:

6 Articles
Health in the Wild

Food Packaging: Unexpected Food Safety Risks you need to know

Botulism is a particularly serious foodborne illness associated with toxins produced by Clostridium botulinum under certain conditions.
Medicine without Jargon

The Best Birthing Position: What Current Evidence Says

Although it has become less common in countries with ready access to obstetric care, obstructed labor remains one of the leading causes of maternal...
The Hard Parts of Medicine

Do You Need Supplements? What Medical Research Says

An inadequate supply of these nutrients can impair normal body function and, in some cases, cause serious illness.
Unstraight Lines

The Convenience of a Label

We name the wound before we know the pain, the illness before the person, the mistake before the story.
The Hard Parts of Medicine

Polypharmacy: What Really Happens When You Take Multiple Medicines

Longer life expectancy, the increasing number of people living with chronic diseases, improved medical treatment, and the use of medicines to prevent future illness...
Cases & Narratives

His Last Malaria: A Case of Suspected Fake Medicines

He was young, otherwise healthy, and had been through the illness before.